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Copyright 2011 Rocky Mountain Rider. ALL RIGHTS RESERVED. Reproduction of any editorial material, artwork and photos is strictly forbidden without express written permission of the publisher. For information about reprint rights, please contact the editor;


Water Requirements of Horses

By Heather Smith Thomas, Salmon, Idaho


August 2011 issue


      Water should always be available to horses; it is essential for digestion and waste elimination. The body’s chemical reactions, cellular reactions, transporting of nutrients and wastes, temperature regulation, joint lubrication, shock absorption in body cavities and joints, all depend on water. It also plays a major role in temperature control, through sweating.

      The horse’s stomach holds only three to four gallons of water — about as much as he will drink at one time when thirsty. A 1,000 pound horse drinks about 10 to 12 gallons of water daily in mild weather, the actual amount depending on his work and the day’s temperature.

      During 90- to 100-degree weather, the idle horse drinks at least 16 gallons to replace fluid lost through sweat; a working horse drinks much more. With heat and work (or hot weather and lactation), water consumption may exceed 100 gallons a day. When daytime temperatures drop below freezing, most horses drink only four or five gallons daily. These are just averages; individual horses may consistently drink more or less than these amounts.

      Often the first concern in any disease condition is to make sure the horse has enough body fluid, since dehydration can have serious consequences. Lack of water affects all body functions, and can be caused by the horse not drinking enough, or by excessive water loss. Fever, diarrhea, excessive sweating, and other factors can reduce the body’s water supply.

      Water is the most important ingredient of a horse’s diet. He can live much longer without food than he can without water. A study in 1982 showed that horses in a warm climate could survive 20 to 25 days without feed, if they had water to drink. But when deprived of water (even though they had plenty of feed), they lived only five or six days —and stopped eating by the second day.

Water Requirements for Horses by Heather Smith Thomas


Fluid Status and Dehydration —

      When a horse is short on fluid, the first sign of this imbalance may be colic; water is pulled from the gut to service more important functions. If he continues to be short on water, more serious problems arise. If dehydration is gradual, the first sign may be decrease in appetite, and impaction; there is little moisture in the digestive tract. Feces become scanty and hard. The horse won’t eat, and passes little manure. To prevent colic and more serious problems, the horseman should make sure a horse has access to plenty of clean, fresh water, and should become aware of early warning signs of dehydration.

      The pinch test can give a clue to the horse’s fluid status. This involves pulling out a pinch of loose skin at the point of the shoulder. Upon release, the skin should snap right back into place immediately. If it takes two to three seconds to sink down, the horse is moderately dehydrated (loss of fluid in and around the tissue cells; the skin is less elastic). If it takes more than five to seven seconds to sink back into place, he’s severely dehydrated.


Daily Requirements —

      The water requirement for any horse consists of the total sum of water lost to the body, plus the amount of water needed for specific functions such as building body tissues or producing milk.

      The average adult horse (idle, doing no work) needs 10 to 15 gallons of water per day — and more in hot weather, or when lactating. Much of this daily requirement is obtained by drinking, but part can be supplied by moisture in feeds such as green pasture plants, and water generated in the body or recycled as saliva.

      An adult horse produces six to seven gallons of saliva daily while eating (from fluid pulled out of the bloodstream) and this moisture later leaves the gut — recycled back into the bloodstream. Water loss occurs through sweat, evaporation through the skin, in urine, manure, and moisture lost through the lungs while breathing.

      The specific water requirements of any horse will be greatly influenced by weather and air temperature, how much the horse is exerting and sweating, and what type of feed is eaten. Lush green grass may be 50 to 90 percent water, while hay may be only five to eight percent water. Water consumption is closely related to dry matter intake, and salt consumption. Nutritionists estimate that the minimum amount of water required by the non-working horse in a moderate environment (not very hot nor cold) is about 1.5 quarts of water per pound of dry matter eaten. Horses eating hay will drink more water than horses consuming a large grain ration and less hay.


Water Requirements for Horses by Heather Smith Thomas

      In one study, water consumption rose as high as a gallon per pound of dry matter intake when air temperature reached 100 degrees. Horses exerting strenuously in hot weather may lose 10 gallons or more in sweat (some may lose 3 to 4 gallons per hour); they may lose 5 to 10 percent of body weight in fluid loss. If a horse loses 10 percent of his body water, he’s at risk for digestive disturbances. Loss of 20 percent of body fluid is fatal.

      To avoid dangerous water loss in summer, don’t work a horse hard when temperature and/or humidity are high, and don’t withhold water when he’s overheated from exertion. It’s safe to water a hot horse as long as the water is not cold, and as long as he continues exercise after drinking (such as walking him after his work). Ice- cold water may cause intestinal cramping and muscle problems if the horse stands idle after drinking, with his blood rushing from the muscles to warm cold water in his gut. Lukewarm water is always safer.

      Water that sits in a tank out in the sunshine may get too warm, however, and horses will refuse to drink it. Most horses prefer water below 75 degrees F. In hot weather, situate water tanks and tubs in shady areas.

      Estimates of how much water a horse needs are only guidelines, since every horse is different. Many factors influence water consumption. One study documented daily water intake of one horse for a year. The wide variation in his consumption (a low of 2 gallons and a high of 20 gallons per day) illustrates the fact that there is no standard. The best situation is to provide easy access to plenty of fresh, clean water at all times, with the water being warmed during severely cold weather.


Heather Smith Thomas is the author of numerous articles and 20 books. She and her husband ranch near Salmon, Idaho . For more information about her books, visit

     Heather’s blog online is:


Copyright 2011 Rocky Mountain Rider. ALL RIGHTS RESERVED. Reproduction of any editorial material, artwork and photos is strictly forbidden without express written permission of the publisher. For information about reprint rights, please contact the editor;


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